WordNet sense 1 (genus of small erect or climbing herbs with pinnate leaves and small inconspicuous white flowers and small flattened pods: lentils):

genus Lens

WordNet sense 2 (biconvex transparent body situated behind the iris in the eye; it focuses light waves on the retina):

crystalline lens

WordNet sense 3 (electronic equipment that uses a magnetic or electric field in order to focus a beam of electrons):

electron lens

WordNet sense 4 (a transparent optical device used to converge or diverge transmitted light and to form images):

lense, lens system